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WAEC Mathematics 1988 Question 17

Question 17

Graphs of Functions

A student is told to draw the graph of y = x2 + 4x − 6. He is then told to draw a linear graph on the same axis such that the intersection of the two graphs will give the solutions to the equation x2 + 4x − 7 = 0. What is the equation of the linear graph he needs to draw?

  1. A.x = 1
  2. B.x = −1
  3. C.y = 1
  4. D.y = −1
  5. E.x + y = 1
Show the answer and explanation

Answer: C (y = 1)

Explanation

x2 + 4x − 7 = 0 is the same as x2 + 4x − 6 = 1, so the line needed is y = 1.